Reversible current-steering switch



s. y MARKOwlTz REVERSIBLE CURRENT-STEERING SWITCH I Filed March 9. 1959 Oct. 30, 1962 Unite States This invention relates to electronic switching devices employing magnetic cores, and, more particularly, to improvements therein.

A magnetic-core memory is described and shown in an article by William M. Papian, entitled The MIT Magnetic Core Memory, which is printed in the Proceedings of the Eastern Joint Computer Conference, Washington, D.C., December 1953. This type of magnetic-core mernory requires the solution of a switching problem for its operation. This switching problem is of the type wherein current must be directed through `one of very many loads. This current must be switched at a high rate between the windings which are coupled to the cores of the memory in order that these cores be driven either for the purpose of the storage of information or for the purpose of the readout of information therefrom. Many different solutions have been presented directed to the switching problem. It was soon recognized that it is more inexpensive to have a single drive-current source with apparatus for directing current from the single drivecurrent source to the desired oneof many loads, rather than presenting a plurality of drive-current sources wi apparatus to turn on the one required'.

An object of the present invention is to provide an improved switching apparatus which enables the switching of current from a single current source rapidly to one of a plurality of loads. f

Another object of the present invention is the provision of a novel and useful sequentialrreversible switch.

Yet another object of the present invention is the provision of a reversible magnetic-core switch which steers current from a single current source sequentially to a plurality of loads.

These and other objects of the invention are achieved in an arrangement wherein a magnetic core is provided for each one of a plurality of loads. Each core is of the type having two conditions of magnetic remanence and being capable of being driven from one to the other condition of magnetic remanence. Windings are provided on these cores whereby all but a first' one of the cores are set in one condition of magnetic remanence this one being set in an opposite condition of magnetic remanence 1). Means are provided for driving this one core to its 0 state of remanence. ln response to the one core being driven and from l to O, a switch means which is associated with this core is enabled to apply current to the associated load and to apply drives to the 1 state of remanence to the preceding and succeeding cores. The preceding core is inhibited from being driven by the same drive as is applied to drive the one core. Thus, only the succeeding core is driven to its 1 sta-te. One load current source is connected to a plurality of the switch means, each of which is connected to a separate load and each of which is associated with and operated by a different core when it is driven from 1 to .0.

mmnice Aiic example, itis desired to` know 3,061,740 Patented Oct. `30, 1962 Means are provided for successively advancing the 1 state of remanence from core to core. A reversal of the sequence of excitation of this means enables a reversal of the l state progression and thereby the load excitation.

The novel features that are considered characteristic of this invention are set forth With particularity in the ap pended claims. The invention itself, both as to its organization and method of operation, as Well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawing, which is a circuit diagram of an embodiment of the invention.

Referring now to the drawing, which shows an embodiment of the invention in circuit-diagram form, the invention includes a plurality of magnetic cores, respectively numbered 1, 2, 3, 4, 5 (N-l), and (N). These cores are represented by rectangles, and the windings which are `coupled thereto will be represented by coils which intersect with these rectangles. Each magnetic core has inductively coupled thereto a clear winding 1A, 2A, etc.V These clear `windings are all connected in series to a clear signal source 10. However, a clear Winding 1A on the rst core, as may be seen from the drawing, is excited in reverse to the manner of applying excitation to the other windings on the cores. Thus, a clear signal current flowing through the series clearwindings drives Ycore l'with a polarity which is `reverse from the polarity of the drive applied to all the other cores.

Three advancing lines 11,

12, and 13are employedfoij controlling lthe operation progression of the switch.

These lines have signals: successively applied ,thereto from athree-stage, reversible counter 2t).` Advance line 411 has connected in series thereto iirst advancing windings 1B, 3B,'4B (N-1)B, and (VN)B.' These advance windings are coupled to the core Whose reference numeral precedes the letter in their identication .reference-characters. The second drive winding 12has connected in yseries therewith a plurality of second advancing windings '1 C, 2C, 4C, 5C )C. The third drive line 13 has connectedl seriestherewith third advancing windings 2D, 3D, 5D v. `(N-,l),D.`

Whether or notan advancingtwinding is to be coupled to a core may bevreadilyrdetermined by rst adding one to the number of that drive line. This sum is subtracted from the number of the core inthe sequence. The difference is divided .by three, and, if the lquotient is a whole number, there is no advance winding on that core for the particular drive line in question. Totake a speciwhether or not there is to be an, advancing winding for the second drive line on the 25thcore. Adding one to the number of the second drive line, which is two, produces three as the sum. Subtracting 3 from 25 provides 22; 22 divided by 3 is not an integral number, and therefore there will `be a drive winding on the 25th core for the second drive line. If it is desiredto nd out whether or not the third drive line has a winding on the 25th core, then 3}1=4, 25 4:21, 3\/21=7, an integral number, and therefore there will not be an advancing'winding on the 25th core for the `third drive line.

The above information may be more succinctly stated in a converse form. For the rst drive line, an advancing winding is provided on every core except those. on the cores whose number in the ordered succession is 3K-l-2, where K equals any positive integer or zero. For the second drive line, 3K-l-3 is used, and for the third drive line 3K+l is used. Thus, inthe example above, where K is 7, there is no winding for the tirst drive line on the 23rd core, none on the 24th core for the second drive line, and none on the 25th core for the third drive line.

Another winding which will be inductively coupled to all cores but the rst is a forward-count winding 2E, 3E, 4E, 5E (N-1)E, and (N) E. A reverse-count winding 1G, 2G, 3G, 4G, 5G (N-1)G is inductively coupled on every core except the last, or the Nth core. The last winding on every core is an output winding 11F through NIF.

A separate transistor 1T, 2T, 3T, 4T, 5T, (N-1)T, (N)T is associated with each separate core. The collector of transistor of 1T is connected through a voltagelimiting resistor 22 to a negative current source 24. The collector of each succeeding transistor 2T through NT is connected to this current-limiting resistor through the reverse-count winding, which is on the immediately preceding core to the one with which the transistor is associated. In somewhat similar fashion, the emitter of each transistor I1T through (N--1)T is connected to a separate one of a plurality of loads 2L, 3L, 4L, 5L, (N- 1)L, through the forward-count winding, which is coupled to the succeeding core in the series. Thus, the emitter of .transistor 1T is connected through the forward-count winding 2E to the load 1L. The emitter of transistor 4T is connected through the forward-count winding 5E to the load 4L.

The emitter of each transistor 1T through NT is con nected to its base through the respective output windings I1F, 2F N-F, and through respective resistors 1R- NR. The purpose of the emitter-base connection is to insure that in the quiescent, or standby, condition none oi the transistors 1T through (N)T will conduct current. However, when a voltage is induced in an output winding, due to the associated core being driven yfrom its one state of magnetic remanence to its zero state of magnetic remanence, then this voltage is applied between the emitter and base of the associated transistor with a polarity to enable the transistor to conduct in saturation. When this happens, the transistor lfunctions in the manner of a closed switch, Current is drawn from the negativecurrent source through a reverse-count winding, if the transistor is other than the first transistor, then through the transistor and a forward-count winding, and then through the load. It should be noted that the reference numeral selected `for indentifying the various components of this invention have been selected to provide a ready association of a core which is being driven with its windings, transistor, and load.

The invention, whose connections have been described above, operates as follows. At the outset a pulse is applied lfrom the clear signal source through the clear line to all the clear windings, which, as a result, drive the iirst core to its 1 state of remanence and all the other cores to their 0 states of remanence. Thereafter, the reversible counter is permitted to start counting. It irst energizes the yfirst drive line, whereby the drive windings 1B, 3B, 4B (N-1)B, (N)B receive current which tends to drive the cores with which these windings are inductively coupled to their 0 state of magnetic remanence. As a result, only the core in its 1 state, which now is the iirst core, is driven in response thereto, which induces a voltage in the associated output winding 1F. This enables transistor 1T, whose emitter is made positive with respect to its base thereby, to draw current from the negative-current source. This current flows through the transistor 1T through the forward-count winding 2E and then through the load 1L. The forward-count winding 2E applies a drive to the second core to drive it from its 0 toits l state of magnetic remanence.

The reversible counter then applies a driveto the second drive line 12. This drive can only drive core 2 back to its remanence at its 0 state, since the other cores in the switch are already in their 0y state. As a result, transistor 2T is enabled to become conductive. Transistor 2T has a reverse-count winding in series with its collector. This reverse-count winding tends to drive core 1 to its state of remanence in condition 1. However, because of the presence of drive winding 1C, lwhich is tending to drive 1 to its 0 state of remanence, the eect of the reverse-count winding is nullitied and core 1 remains in its 0 state of remanence. Transistor 2T has the forwardcount winding 3E in series therewith and will therefore drive the third core toward its l state of magnetic remanence while applying current to the load 2L.

The reversible counter 29 then applies a drive to its third drive line 13. This, by operation of the winding 3D, will drive the third core back to the 0 state of magnetic remanence. This induces an output in the output winding 3G, whereby transistor 3T is enabled to become conductive. Transistor 3T will thereupon drive the fourth core to its l state as a result of the current being applied to the winding 4E and` will drive the load 3L. The operation of the invention in its advancing mode should become readily apparent from the above description.

If, after the Nth core has been driven to its O remanence condition as a result of the advancing operation, it is desired to operate the switch again in its advancing mode, then a clear signal must be applied to reset core 1 to its l state of remanence to commence ,the advancing operation again. However, if it is desired to reverse the switch, then, if such reversal is .to occur at .the end of a complete advance progression, no clear signal is applied, but instead the reversible counter operation is reversed. Thus, if the last drive line that -Was energized was drive line 113, which set core N in its 1 state of remanenca'then for reversing the operation of the switch the reversible counter is driven to next energize drive line 12.

At this point, it should be noted -that due to the pattern established for advancing windings and their connection to the drive lines, when drive line excitation is reversed there is no inhibiting action provided for a succeeding core but only for the preceding core in this reverse progression mode of operation. In other words, the operation of the system is the same in both directions. The direction of operation is determined solely by the sequence of drive line excitation. The reversing operation can be commenced at any time without going to the last core in the progression by the expedient of reversing the order of drive line excitation. For the example given, core N is in its l state. Excitation of drive line '11 in the advance mode of operation would drive core N to its 0 state. Drive line 12 is energized for reversal of the switch. This causes the core N to be driven to its 0 state, as a result of which its associated transistor draws current through the reverse-current winding (N-1)G. This tends to drive the (N-1) core to its 1 state of remanence. This latter drive is now unopposed, and the (N-ll) core can attain the i1 state.

For a further illustration of the reverse mode of operation, consider the situation when core 4 is in its 1 state at the time such reverse mode of operation is desired. This means that the last drive line excited was 13. Excitation of drive line 12, instead of 11, drives core 4 from 1 to 0. Transistor 4T is rendered conductive, exciting load 4. The drive current passing ythrough forward-drive winding 5 is opposed by the current passing through coil 5C. However, reverse-count winding 3G can unopposedly drive core 3 to its l state. Drive line 11 is excited next. This returns core 3 to its 0 state, which results in load 3 being excited and core 2 being driven to its 1 state.

There has accordingly been shown and described herein a novel and useful reversible switching device which sequentially energizes one of a plurality of loads -from a single current source. l

1. A switch for directing current from a load current source sequentially -to each one ofaV plurality of separate loads comprising a plurality of magnetic cores in an ordered succession, the number of cores in said plurality being one more than the number of separate loads, each core having two states of magnetic remanence respectively designated las the and l state and being capable of being driven from one to the other state, means for establishing a first of said plurality of cores in its one state of magnetic remanence and the remaining cores in their zero state of magnetic remanence, a different output winding coupled to each core, a different iirst winding for all cores except the first in said ordered succession each of which is coupled to an associated core, a different second winding for all cores except the last in said ordered succession each of which is coupled to an associated core, each of said lirst windings having one of their ends coupled to a different one of said plurality of loads, each said second windings having one of their ends coupled to said source of current, a plurality of normally open switch means each of which is associated with a different core, means coupling the normally open switch means associated with the irst core in said progression between said load current source and the other end of the rirst coil associated with the succeeding core, means coupling each of the normally open switch means associated with all but the last core between the other ends of the rst and second windings respectively associated with a core succeeding and preceding the core with which each normally open switch means is associated, means for applying a drive to a core in its one state and to the preceding core to drive them to their zero states of remanence to thereby induce a voltage in the output winding associated with the driven core which was in `the one state wherein said means for applying drive to a core in its one state and to the preceding core to drive them to their zero states of remanence includes a first, second, and third drive line, a rst advance winding coupled to every core, a second advance winding coupled to every core, means connecting in series with the first drive line one of the advance windings on all of the cores except those on the cores whose number in the ordered succession equals 3K-l-2, where K equals any positive integer or zero, means connecting in series with the second drive line one of the advance windings on all of the cores except those on the core whose number in the ordered succession equals 3K-I-3, means connecting in series with the third drive line the remaining one of the advance windings on all of the cores except those whose number in the ordered succession equals 3K-i-l, means vfor applying a drive signal in a desired succession to said first, second, and third drive lines, and means responsive to a voltage induced in an output winding to close the normally open switch associated with the same core to enable current to yflow through the normally open switch and the Afirst and second windings between which it is coupled to the load and to apply a drive to the one state to the succeeding and preceding cores.

2. A switch for directing current from a load current source sequentially to each one of a plurality of separate loads comprising a plurality of magnetic cores in an ordered succession, the number of cores in said plurality being one more than the number of separate loads, each core having two states of magnetic remanence respectively designated as the 0 and 1 state and being capable of being driven from one to the other state, each core having inductively coupled thereto a clear winding, two advancing windings, an output winding, a forward-count winding on all but the first core in said ordered succession, and a reverse-count winding on all but the last core in said ordered succession, means connecting all said clear windings in series with the clear winding coupled to the iirst of said cores being connected in a sense reversedl from that of said other/*clear windings, rst, second, and third drive lines, means connecting in series with the first drive line one of -the advancing windings on all of the cores except those on the cores whose number inthe ordered succession equals 3K-l-2 where K equals any positive integer or zero, means connecting in series with the second drive line one ofthe advancing windings on all of the cores except those on the cores whose number in the ordered succession equals 3K-I-3, means connecting in series with the third drive line the remaining one of the advancing windings on all of the cores except those whose number in the ordered succession equals 3K-|-*1, a separate normally open switch means associated with each core, means coupling the normally open switch means associated with said irst core between said source of load current and one end of the forward-count Winding of a succeeding core in said ordered succession, means coupling each reversecount winding between said load current source and one side of a normally open switch means associated with a core succeeding the one with which said reverse-count winding is associated, means coupling the other side of each normally open switch means except the one associated with the first core to one side of the lforwardcount winding associated with an immediately succeeding core, means connecting a diierent load to the other end of a different one of said forward-count windings, means for applying a clear signal to said series-connected clear windings -to drive one of them to its 1 condition of remanence, means for applying a drive signal to one of said first, second, and third drive lines to thereby shift the core in the 1 state of remanence to its zero state, and means for each normally open switch means responsive to a core being driven from its one to its zero state of remanence to close the normally open switch means associated with that core to thereby draw current through said connected reverseand forward-count windings and through the load connected to the forwardcount winding.

3. A switch for directing current -from a load current source sequentially to each one of a plurality of separate loads comprising a plurality of magnetic cores in an ordered succession, the number of cores in said plurality being one more than the number of separate loads, each core having two states of magnetic remanence respectively designated as the `0 and l state and being capable of being driven from one to the other State, each core having inductively coupled thereto a clear winding, two advancing windings, an output winding, a forward-count winding on all but the lirst core in said ordered Isuccession, and a reverse-count winding on all but the last corev in said ordered succession, means connecting all said clear windings in series with the clear winding coupled to the irst of said cores being connected in a sense reversed from that of said other clear windings, `first, second, and third drive lines, means connecting in series with the first drive line one of the advancing windings on all of the cores except those on the cores whose number in the ordered succession equals SK-i-Z where K equals any positive integer or zero, means connecting in series with the second drive line one of the advancing windings on all of the cores except those on the cores whose number in the ordered succession equals 3K-I-3, means connecting in series with the third drive line the remaining one of the advancing windings on all of the cores except those whose number in the ordered succession euals 3K-I- l, a separate transistor associated with each core, each having a collector, emitter, and base electrode, means connecting each reverse-count winding between said load current source and the collector of a transistor associated with a core succeeding the one associated with the reverse-count winding in said ordered succession, means connecting each `forward-count wind- 7 ing between a separate load and the emitter of a tran- References Cited in the file of this patent sistor associated with a core preceding .the core associ- UNITED STATES PATENTS ated with the forward-count winding 1n said ordered succession, means coupling each output winding between 119241494 Avery 111116 24, 1958 the emitter and base of the transistor associated with 5 21591405 Cartel' APR 1, 1952 the same core as said output Winding, means for apply- 2,7191961 Kalmaugh OC- 5, 1955 ing a clear signal to said series-connected clear windings, 2,785,390 Ralchman Mal'- 121 1957 and means for applying a drive signal in a desired suc- 21891170 P31111 June 15, 1959 cession to said iirst, second, and third drive lines to there- OTHER REFERENCES by enable said transistors to apply current to said plulo amy of 10a ds in a desired Succession' Magnetlc Commutator Switch by Brlggs and Lo, RCA

TN No. 110, March 12, 1958. 

